SYSTEMIC DRY COW THERAPY - A PRELIMINARY-REPORT

Efficacy of three different treatment regimens in the elimination and prevention of Staphylococcus aureus intramammary infection was studied in 106 dry cow periods. At drying off, norfloxacin nicotinate was given subcutaneously to 44 cows at 10 mg/kg, oxytetracycline-HCl was administered intramuscularly to 18 cows at 20 mg/kg, 500 mg cephapirin benzathine were infused into each udder quarter of 21 cows, and a group of 23 cows served as an untreated control. Number of existing Staphylococcus aureus intramammary infections was reduced only in the norfloxacin nicotinate treatment group. New infection rate appeared lower in the two systemic treatment groups. The percentage of infected quarters remained the same throughout the dry period in the norfloxacin treatment group but number of infected quarters increased by 33 to 85% (significant in the cephapirin group) in the other groups. Minimal inhibitory concentration of the drugs for 57 S. aureus isolates was determined. Isolates were sensitive to norfloxacin and cephapirin and moderately sensitive to oxytetracycline. Results suggest that systemic dry cow therapy using norfloxacin nicotinate, which possesses large distribution volume, long half-life, and is highly active against the pathogen involved, was more effective than the other treatments. © 1990, American Dairy Science Association. All rights reserved.